1. Field of the Invention
The present invention relates to boarding steps and ladders for heavy equipment, such as earthmovers, and more specifically to an easy-to-use, flexible boarding ladder.
2. Description of the Related Art
Job sites are harsh environments for machinery, and place great demands on their structural integrity. Dust, rocks, and other hazards exact a toll on man and machine alike. Much has been accomplished to make the machines more capable and more durable than ever before, but there are numerous technical areas that need advancements. Ergonomics and human factors often clash with the realities of mechanical engineers as they strive to make good machines better. One of these areas relates to human ingress and egress from the machines, such as large dump trucks and loaders used in mining operations.
The cabs of those vehicles have advanced a long way from the early days, but the operators still need to climb up into the cab. Often, the path to the cab is quite dangerous. The most common ingress method is a metal ladder that is attached to the side of the vehicles. The ladders are quite functional, and serve their purpose on the most basic level. However, while these ladders are rigid and strong enough to withstand the weight and abuse of the vehicle operators, they are often damaged or destroyed by the conditions outside of the cab. A damaged ladder can make egress a dangerous proposition, particularly where the vehicle is very tall or the ground is uneven.
Ladders are typically oriented as close to the cab as is possible to provide a more direct route to the cab and to minimize the exposure of the operator to the hazardous conditions. On most vehicles, this means that the boarding ladder is quite close to a front wheel of the vehicle. While the vehicle is in motion, the turning wheels kick up rocks and debris, particularly at unimproved job sites. Mud flaps and rock guards are not really an option for a couple of reasons. Such guards could collect debris and interfere with the operation of the vehicle. Also, the guards would need to be prohibitively heavy and expensive to prevent their being damaged and becoming an impediment to vehicle operation. Another factor is that vehicle operators often make mistakes and run into things, such as rocks, buildings and other vehicles. The reality is that boarding ladders will remain exposed to the elements and harsh conditions. Another reality is that access systems require a degree of compromise between what is desirable and what is practicable.
Compared to large rocks and debris, boarding ladders are relatively flimsy, even when the bottom step is suspended from a steel cable, and it won't be long before it is bent, broken, or even knocked off. Thus, a flexible boarding ladder will last a lot longer than a rigid one. However, some flexible ladders, such as rope ladders, even using steel cable, can be difficult to climb, up or down. It is unacceptable for an operator to miss the step on a rope ladder and fall 4 or 6 feet to the ground. Remember, the objective of most companies is to get the job done, efficiently and without injuries. Some solutions have replaced the bottom six or so steps of a rigid boarding ladder with a hydraulically operated section that can be swung up out of harms way when the vehicle is in motion. Such devices are quite complex. They need to be linked to the vehicle's engine and controls so that the operator cannot drive away with the ladder in the down position, and they need to provide controls in both the cab and at the base of the ladder for ingress and egress. It is an expensive solution, compared with an ordinary ladder.
Therefore, there has been and continues to be a need for a boarding ladder with the damage-resistance and longevity of a flexible rope or cable ladder, and the sure-footed safety of a rigid boarding ladder.